Reuse of waste glass powder in alkali-activated metakaolin/fly ash pastes: Physical properties, reaction kinetics and microstructure

To better understand the reaction of waste glass powder (WGP) as precursor in geopolymerization process, the leaching of main active ions (Ca²⁺, Al³⁺ and Si⁴⁺) from waste glass powder in alkaline solution was evaluated. The roles of replacement of metakaolin (MK) by WGP on the alkali-activated material (AAM) pastes were investigated by physical properties, reaction kinetics and microstructure. Experimental results show that the active ions are efficiently dissolved and leached in sodium hydroxide solution. With the incorporation of WGP, the workability of pastes is improved due to the physical and chemical characteristics of WGP particles. The mechanical performances including strengths and volume density are enhanced and obtained the highest values at the 20 wt% substitution level of MK by WGP. From the isothermal calorimetry (ICC), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) results, the geopolymerization process is accelerated and additional binder gels are formed. These are attributed to the reactive components (especially CaO) in WGP. The analyses of mercury intrusion porosimetry (MIP) and scanning electron microscope and energy dispersive spectrometer (SEM-EDS) indicate that the denser microstructure originated from the enrichment of gels and filling effect of raw materials particles is the significant support for the development of mechanical properties of AAM pastes.